Field measurement of particle-size dependency in concentration changes of indoor particulate matter during ventilation with opening window

We conducted a field study to measure particulate matter (PM) concentrations for particles with diameters ranging from 03 to 10 μm in size. The study was conducted ma room of an office building i n Tokyo, over a three -week period. Occupan ts in the room utilized natural ventilation by manually opening a window. Because the outdoor PM had a higher concentration than that indtx)rs, employing natural ventilation leads to larger IndootfOutdoor (I/O) concentration ratios. Increases (decreases) in PM concentrations wen: observed just after opening (closing) th: Window. Concentration changes were even more remarkable for PM consisting of larger particle size. We found that this particle-size dependency in the concentration changes caused by the natural ventilation could be explained quantitatively in teims of thcdtfference in the gravity-settlement velocity of the particles.